Front access packing arrangement and a packing assembly installation and removal method

ABSTRACT

A packing arrangement and a method are disclosed, in which a packing assembly of a reciprocating plunger pump is accessible, removable and adjustable from the front end of the fluid-end. As the inside and outside diameter of the packing rings define the area on which the pressure is exerted and results in the total force on the packing arrangement, a packing arrangement with a smaller outside diameter can be advantageous as the forces are reduced and a longer packing life can be expected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional application No. 63/176,411, filed Apr. 19, 2021 which is incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a packing arrangement and a packing assembly installation and removal method for a reciprocation high pressure plunger pump the packing assembly being accessible, replaceable and adjustable from the front end of the plunger pump.

BACKGROUND

In the field of high pressure reciprocating pumps used in oil and gas well drilling and production enhancement operations maintenance on the fluid end is often cumbersome and under time constraints as daily pumping hours continue to increase as well as the demands on the pumps itself.

The object of the invention is to provide a new packing arrangement and method for packing installation to improve the maintenance time and effort to replace a packing seal arrangement and provide additional support for the plunger.

In conventional reciprocating plunger pumps access to its packing arrangement is obtained only from the backside i.e. from between the power-end and fluid-end which makes it cumbersome to replace the packing arrangement. Removal and installing of the packing arrangement in triplex or quintuplex requires a sideway access and for intermediate plungers the adjacent plungers also need to be removed to allow access for disassembly of the intermediate packing arrangements

Most of these packing arrangements consist of a number of so called V-shaped or Chevron type packing rings with at one end an adapter ring with a profile matching the V-rings and on the opposed side a lubrication gland to provide back up for the elastomer and to provide lubrication as indicated in FIGS. 1A and 1B. The V-rings can be of various material and hardness depending on the pumping application.

They all have in common that some initial axial mechanical force needs to be applied to compress the V-rings and to initiate sealing where the distinctive V-shape creates a hinge-like action of each V-ring and causes immediate reaction even to minor pressure changes. Each individual lip of a V-packing set independently reacts to pressure and automatically affects a seal.

The multiple lip configuration automatically distributes pressure and an effective seal along the plunger.

SUMMARY OF THE INVENTION

This invention discloses a packing arrangement and a method where the packing assembly of a reciprocating plunger pump is accessible, removable and adjustable from the front end of the fluid-end instead of the rear end.

Forces exerted on the packing arrangement as described in the previous embodiments and in general for reciprocating pumps is directly related to the size of the packing rings and the pump pressure. Packing arrangements as used in oilfield services pumps are minimal ½ inch in thickness i.e. for a 4½ inch plunger the outer diameter of the packing is 5½ inch.

As the inside and outside diameter of the packing rings define the area on which the pressure is exerted and results in the total force on the packing arrangement a packing arrangement with a smaller outside diameter then used in well services pumps can be advantageous as the forces are reduced and a longer packing life can be expected.

Table I Shows the Difference in Forces at a Reduced Packing Outside Diameter

Forces on the packing arrangement at reduced packing outer diameter Pressure, psi 10000 Standard area Slim area packing packing Plunger diameter, inch 4.5 15.904 4.5 15.904 Packing OD, inch 5.5 23.758 5 19.635 Packing area, sqin 7.854 3.731 force on packing, lbs 78540 37306

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B schematically show prior art packing arrangements comprising a number of so called V-shaped or Chevron type packing rings;

FIG. 2 schematically shows a prior art embodiment of a crankshaft driven reciprocating positive displacement plunger pump;

FIGS. 3A and 3B schematically show an embodiment of a pump with a front end packing access;

FIG. 4 schematically shows another embodiment of the invention;

FIG. 5 schematically shows another embodiment of the invention;

FIG. 6 schematically shows another embodiment of the invention;

FIG. 7 schematically shows another embodiment of the invention;

FIG. 8 schematically shows another embodiment of the invention;

FIG. 9 schematically shows another embodiment of the invention;

FIG. 10 schematically shows another embodiment of the invention; and

FIGS. 11A and 11B schematically show further embodiments of the invention.

DETAILED DESCRIPTION

In the enclosed drawings some exemplary embodiments of the invention are shown schematically.

In FIG. 2 , a prior art embodiment of a crankshaft driven reciprocating positive displacement plunger pump is shown with a conventional packing arrangement 8 comprising an adjustment nut 8 a, lubrication gland 8 b, set of V-rings 8 c and adapter ring 8 d. Disassembly of the packing arrangement 8 requires the removal of the front end cover 7, the plunger 3 and adjusting nut 8 a upon which the packing arrangement 8 can be moved backwards out of the fluid end body 2. The spacing of the power-end 1 to fluid-end 2 bolts 9 and the outside diameter of the packing adjustment nut is often such that the adjustment nut 8 a and packing arrangement 8 can only be removed sideways and therefor adjacent plungers needs to be removed as well in order to remove the adjustment nut 8 a and the packing arrangement 8 of the intermediate plungers of a triplex or quintuplex type pump.

During a discharge stroke of the plunger 9 with suction valve 5 closed and discharge valve 6 opening against line pressure the pressure inside of the suction/discharge chamber 4 will create an axial force on the packing arrangement 8 equal to (packing OD²−packing ID²)×PI/4×pressure. This axial force is directed backwards and needs to be absorbed by the lubrication gland 8 b and packing adjusting nut 8 a threaded to the fluid-end body 2. Axial adjusting of the packing arrangement 8 is achieved by rotating the packing adjustment nut 8 a clockwise viewed from the power-end 1 side. With pressure inside chamber 4 the torque to be applied to the adjusting nut 8 a needs to overcome the force created by the internal pressure on the packing arrangement 8 to achieve a proper sealing initiation and also keeping the packing arrangement 8 in place to prevent it from moving in its cavity.

The high force prohibits many times the adjustment of the packing arrangement 8 during an operation discharge stroke and adjustment can normally only be done with no internal pressure in the pump chamber 4 i.e. during operation on a suction stroke only where with zero pressure in the chamber no force is exerted on the packing arrangement 8.

In FIGS. 3A and 3B, an embodiment of a pump with a front end packing access according to the invention is shown. In comparison to the prior art embodiment shown in FIG. 2 the backward facing force exerted on the packing arrangement 16 comprising a lubrication ring 16 a, set of V-rings 16 b and an adapter ring 16 c is now directly absorbed by the body of the fluid end 10 instead of the adjusting nut. Internal pressure in the pump chamber will force the packing arrangement 16 towards the back of the seal cavity and the keeping in place and adjustment of the packing arrangement 16 is done by means of a sleeve 11 or cage 11 a fitted in the suction chamber 12 of the fluid-end 10. The sleeve 11 is fitted with openings 17, 18 for fluid entry and discharge from and to the valve arrangements. A pin or setscrew 19 will prevent the sleeve to rotate and keep the openings 17, 18 aligned with the suction 18 a and discharge 17 a valve openings.

Adjusting of the packing arrangement is done by rotating one or more studs 15 located in the front end cover 14 which will push back the sleeve 11 or cage 11 a towards the packing arrangement 16 and press and hold it into place.

A pressure present in the suction/discharge chamber 12 will act across the packing arrangement 16 area (packing OD²−packing ID²)×PI/4×pressure) and the subsequent force will force the packing arrangement 16 backwards in the cavity and initiation and adjusting of the packing arrangement 16 can be done without having to overcome the force created by the internal pressure.

The space between the power-end end and the fluid-end which is required for the plunger to make its stroke but no longer needed for the adjusting nut and packing arrangement removal can now be used to provide additional guidance and support 27 for the plunger and therefor prolong the packing life. It also provides an option to install a cooling gland (not shown).

In FIG. 4 , another embodiment of the invention is shown in which when compared to the embodiment shown in FIGS. 3A and 3B the adjusting studs 21 are instead fitted with a wrench connection equipped with tooth wheels which engage with a matching internal toothed wheel 20 covering all of the fitted studs. Rotation of the outer internal toothed wheel 20 will rotate the studs 21 simultaneously and uniformly causing an equal distribution of the forces generated by the studs 21. Due to the gear ratio between the stud 21 teeth and the internal tooth wheel very little effort is required to adjust the packing arrangement 16.

The width of the outer toothed wheel 20 is such to accommodate the axial movement of the studs to reach full adjustment.

In another embodiment of the invention shown in FIG. 5 , a sleeve 11 or cage 11 a is shown with a front end cover 22 with a single bolt 23 to adjust the packing arrangement 16.

A further embodiment of the invention is shown in FIG. 6 , which shows a sleeve 11 or cage 11 a with a front end cover 25 with an integrated hydraulic cylinder 26 to adjust the packing arrangement 16.

In a further embodiment of the invention shown in FIG. 7 , a sleeve 11 or cage 11 a is shown with a front end cover 27 without adjustment provision. The adjustment is achieved by inserting rings 27 a of certain thicknesses as required between the frontend cover 27 and sleeve 11 or cage 11 a.

In another embodiment of the invention shown in FIG. 8 , a packing removal tool is shown consisting of two half-moon segments 28 with extrusions that match recesses in the fluid-end back plate by which the packing arrangement can be removed without disassembling the plungers. By moving the plungers the upset 28 a on the plunger will push out the packing assembly from its recess.

Existing pumps with a conventional packing arrangement as show in FIG. 2 can with minor machining be adapted to accommodate a front end packing arrangement by extending the packing cavity all the way to the front end of the pump and where the existing adjustment nut can be permanently installed against which the front access packing arrangement can be shouldered and rethreading of the front cover threads to accommodate a new front end cover with adjustment option.

A front end access for a double acting pump is shown in FIG. 9 where the plunger 32 is of equal diameter in both pump chambers 31 and 33 and a pushrod 32 a sized such to obtain a displacement ratio of 2:1. A double acting pump is for example known from EP-3464900B1.

Below a brief description of the operation double acting pump is given.

A stroke to the right i.e. a discharge stroke of plunger 32 in chamber 33 is simultaneously creating an expansion (suction) stroke of plunger 32 in chamber 31. Since plunger 32 in chamber 33 displaces double the volume compared to the expanding volume in chamber 31, 50% of the displaced fluid is used to fill the expanding space in chamber 31 whereas the remaining 50% is displaced simultaneously out of the pump.

A stroke to the left i.e. a discharge stroke of plunger 32 in chamber 31 is displacing already pressurized fluid out of chamber 31 and creating a simultaneous suction (expansion) stroke of plunger 32 in chamber 33. The displaced volume out of the pump during the discharge stroke in chamber 31 equals the volume displaced out of the pump during the discharge stroke of 32 in chamber 33 and resulting in a non-pulsating flow.

Note that chamber 2 is always under pressure.

The packing arrangement 35 for the main plunger 32 is made up of two adapter rings 35 a with opposing sets of packing rings 35 b a and a lubrication gland 35 c in between where adjusting of the double packing arrangements is done by means of a sleeve or cage similar as shown in the embodiment of FIG. 3B.

As chamber 31 in the double acting pump is always under pressure during operation of the pump the packing arrangement will always be pushed towards the front of the fluid-end and the sleeve or cage 36 is required to keep the packing arrangement in its place and put some initial force on the arrangement to initiate sealing. The constant pressure in chamber 31 and subsequent force will keep the packing arrangement 35 in its place. Upon pressurizing of chamber 33 during its discharge stroke the pressure across the packing arrangement will be balanced once the discharge valve 34 opens and as both sides have the same surface areas and are subject to the same pressures the forces on the double packing arrangement 35 are balanced as well. A leaking packing set can be noticed by an increased pressure and flow in the lubrication loop. A set of sensors can be used to monitor these parameters.

As the forces on the sleeve or cage 36 due to the pressure in chamber 35 can be substantial and to overcome these the cage 36 is fitted with multiple rods 37 with a diameter bigger than the clearance between the plunger outer diameter and the chamber internal diameter and wherein the rods 37 with a bigger diameter are positioned in recesses 38 in the fluid end body. This embodiment shows four rods but more or less rods can be used.

In comparison with a sleeve this embodiment will also prevent rotation and more importantly prevent clogging of solid particles behind the sleeve and making it easier to remove the packing arrangement.

An additional advantage compared to a conventional packing arrangement in a double acting pump is that the length of the double acting fluid end body can be shorter and replacement of the packing set becomes easier.

In a single acting pump the packing arrangement is subject to compression during a discharge stroke of the plunger and subject to relaxation during a suction stroke whereas with a double acting pump the packing is always under compression. In order to keep a packing arrangement under constant compression a hydraulic cylinder is incorporated in the front end cover and abuts the sleeve or cage as shown in the inventive embodiment shown in FIG. 10 . The diameter of the hydraulic cylinder protruding into the suction chamber is such that its area subject to the internal or external pressure is approximate the same as the packing arrangement area and calculated as following:

(packing Outside D ²−packing Inside D ²)*PI/4  Packing area:

Sqrt((packing OD ²−packing ID ²)*4/PI)  Resulting hydraulic cylinder diameter:

The hydraulic pressure required to move the cylinder is obtained from the outlet side of the pump either thru a direct line or by means of a diaphragm system. As the effective areas of the packing arrangement and the hydraulic cylinder are the same and each area is subject to the same pressures the forces are also equal.

Upon a suction stroke the external hydraulic pressure from line 43 will tend to push the cylinder 42 into the suction chamber 41 and consequently push the sleeve 44 or cage towards the packing arrangement 45 and with the areas being equal the force exerted on the packing arrangement is the same as the force exerted during a discharge stroke.

During a discharge stroke the internal pressure in chamber 41 is acting upon the area of the packing arrangement but at the same time also on the hydraulic cylinder face 42 b protruding into chamber 41.

This pressure balances against the line pressure acting on the opposite side 42 a and therefore no additional force is exerted on the packing arrangement 45 by the hydraulic cylinder 42 during a discharge stroke.

The amount of compression can be changed by either increasing or decreasing the diameter of the hydraulic cylinder 42.

In the embodiments of the invention shown in FIGS. 11A and 11B configurations are shown with a modular packing arrangement which can be withdrawn or installed in one step. The packing rings and lubrication gland are fitted inside a packing sleeve which is connected to the adjustment sleeve or cage by means of multiple pins fitted in slots in the packing sleeve. The position and the length of the slots and the position of the pins are such that the packing arrangement can be assembled outside of the pump and once installed the packing arrangement can be compressed to a predetermined maximum distance without a pin reaching the end of its slot.

In the embodiment shown in FIG. 11A a packing module for a single acting pump is shown where the lubrication ring is integrated in the packing sleeve 50. The packing rings 51 and adapter ring 52 are preinstalled after which the adjustment sleeve 55 is connected to the packing sleeve by means of multiple pins or setscrews. O-rings are provided to create a seal on the outside of the packing sleeve to the atmosphere. The assembly can be installed as one piece around the plunger and kept in place by means described in the previous embodiments.

In the embodiment shown in FIG. 11B a packing module for a double acting pump is shown where the packing sleeve 60 contains a first packing set 61, a lubrication gland 62, a second packing set 63 and an adapter ring 64. The sleeve is connected to the adjustment cage 67 in a similar way as in the embodiment shown in FIG. 11A.

Summarizing, above a packing arrangement and a packing assembly installation and removal method for a reciprocating positive displacement plunger pump is described which packing arrangement is accessible and removable from the front end of the fluid end body where the spacing and adjustment is achieved by means of a sleeve or a cage which spacing can be adjusted by means of one or more threaded studs rotationally fixed within the pump front end cover or adjustment can be achieved by means of an hydraulic cylinder fitted in the front end cover and where the packing arrangement and front end cover preferably form a coaxial line. The packing and lubrication rings can form an integral part of the adjustment sleeve or cage and can be installed and removed as a whole. The packing arrangement is adjustable by means of two or more toothed studs circumferential situated within a front end cover and which can be simultaneously rotated by a matching internal toothed wheel or by a matching wrench. The packing arrangement can be adjustable by means of a hydraulic cylinder incorporated into the front end cover. The dimensions of the hydraulic cylinder can be such that it provides equal forces on the packing arrangement during a suction and discharge stroke, wherein the hydraulic pressure preferably can be obtained from the pump line pressure (with or without a diaphragm). Optionally, openings can be provided in the sleeve for fluid flow from the suction valve and fluid flow towards the discharge valve.

In the packing arrangement the spacing and adjustment sleeve can further be a cage comprising two fitting rings spaced by means of two or more bars/rods, in which the spacing or distance rods are arranged circumferential to fit in matching recesses in the pump suction and compression chamber. With such a packing arrangement and a packing assembly installation and removal method no plunger disassembly is required to replace the packing arrangement and such a packing arrangement enables additional plunger support. In particular such a packing arrangement and a packing assembly installation and removal method is beneficial for a double acting pump with an equally sized diameter plunger in both pump chambers where the chambers are separated by a double acting packing arrangement accessible thru the front end cover. 

1. A packing arrangement for a positive displacement pump having a plunger that reciprocates within a suction/discharge chamber, and suction and discharge valves for flowing fluid to and from the suction/discharge chamber, said packing arrangement comprising at least one packing ring which is accessible from the front, wherein the packing arrangement is configured for adjustment by an adjustment sleeve or cage that is fitted within the suction/discharge chamber.
 2. The packing arrangement of claim 1, wherein the positive displacement pump comprises a front end cover having one or more adjusting studs that, upon rotation of the adjusting studs, press the sleeve or cage against the packing arrangement.
 3. The packing arrangement of claim 2, wherein rings of various thickness are inserted between the front end cover to press the sleeve or cage against the packing arrangement.
 4. The packing arrangement of claim 2 or claim 3, wherein the front end cover has a hydraulic cylinder incorporated that upon applying pressure to the cylinder, press the sleeve or cage against the packing arrangement.
 5. The packing arrangement of claim 1, wherein the packing arrangement is configured for adjustment by an adjustment sleeve that is fitted within the suction/discharge chamber and wherein the sleeve has openings aligned with openings of the suction and discharge valves.
 6. The packing arrangement of claim 5, wherein the packing arrangement is a modular packing arrangement, and further wherein at least one packing ring and a lubrication gland are fitted within a packing sleeve that is detachable connected to the adjustment sleeve.
 7. A packing arrangement for oil field services pumps comprising a packing arrangement of claim 1, wherein the outside diameter of the packing arrangement is reduced to be smaller than the standard for oil well services pumps to reduce the forces exerted on the packing arrangement.
 8. A packing arrangement for a double acting plunger or piston pump comprising two adapter rings and two sets of opposing packing arrangements separated by a lubrication and leak detection gland
 9. The packing arrangement of claim 8, wherein the packing arrangement is a modular packing arrangement, and further wherein at least two opposed packing rings and a lubrication gland are fitted within a packing sleeve that is detachable connected to the adjustment sleeve.
 10. A positive displacement pump comprising the packing arrangement of claim
 1. 11. A method for pumping a fluid, the method comprising flowing the fluid through the suction/discharge chamber of the positive displacement pump of claim 10, wherein pressure from the pump discharge space or discharge line maintains the packing arrangement in place and keeps an equal force on the packing arrangement during its suction and discharge stroke.
 12. A method for pumping a fluid, the method comprising flowing the fluid through the suction/discharge chamber of the positive displacement pump of claim 10, wherein hydraulic pressure from an external source maintains the packing arrangement in place. 